1. Field of Invention
This invention relates generally to filter devices and, more particularly, to filters for fluid flows having high debris content.
2. Description of Related Art
It is well-known that the mechanical cleaning of a filter surface can be accomplished by having a brush or scraper drag along the filter surface where deposits have accumulated.
In certain configurations, the brush or scraper is mounted at one end between two walls but with a significant portion of the brush or scraper projecting beyond the walls. Such configurations are shown in U.S. Pat. No. 148,557 (Gillespie et al.); U.S. Pat. No. 556,725 (Farwell); U.S. Pat. No. 740,574 (Kohlmeyer) and U.S. Pat. No. 793,720 (Godbe). In conventional filter systems, the particulate contaminants are driven off the filter surface and are deposited in a hopper or tank along with the fluid being filtered, thus discarding large amounts of the fluid being filtered.
The use of a brush, or high speed cleaning spray, disposed between a pair of walls for cleaning a cylindrical filter is known in the art, as is disclosed in U.S. Pat. No. 5,423,977 (Aoki et al.) and U.S. Pat. No. 5,595,655 (Steiner et al.) and Swiss Patent No. 22,863 (Zingg). Another variation employs a backwash that drives the particulate contaminants off of the cylindrical filter, as is disclosed in U.S. Pat. No. 3,338,416 (Barry).
A specialized application of such filters is for fuel oil filtering in ships. Prior art ship fuel oil systems use conventional filter cartridges for cleaning the fuel in-line. However, these filter cartridges require frequent replacement which, in turn, requires the fuel flow to be interrupted during replacement. Interruption of the fuel oil flow will shut down the ship's main engines, thereby rendering the ship incapable of maneuvering. This can be catastrophic where the ship is in tight quarters, e.g., during docking or navigating through narrow passageways, or during storms, or during battle with regard to warships. Furthermore, there are additional costs of having to store sufficient replacement cartridges onboard, the logistics involved in shipping and disposing the cartridges to and from the ship, and the labor costs involved in replacing the cartridges. Examples of strainers that pertain to such environments are those shown in U.S. Pat. No. 6,177,022 (Benenson, Jr. et al.) and U.S. Pat. No. 6,517,722 (Benenson, Jr. et al.).
However, there remains a need for filtering a fluid flow containing a large amount of debris that permits the filter to be cleaned thoroughly while minimizing interruption to the filtering process.
All references cited herein are incorporated herein by reference in their entireties.